Implements speech-to-text (via whisper-cpp) and text-to-speech (via espeak)
functionality with key bindings. Replaces coreutils with busybox for lighter
dependencies and removes explicit buildInputs since all paths are hardcoded.
- Update package description and fix mainProgram typo
- Rewrite documentation to describe project switching, not process viewing
- Add PROJECT_FOLDERS configuration and usage examples
- Update all references across docs (README, guides, module overviews)
